Oxygen electrode studies with human skeletal muscle mitochondria in vitro. A re-appraisal

Polarographic measurement of respiration rates in skeletal muscle mitochondria is a valuable research tool in human disease but the data on normal muscle are sparse and conflicting. In this study, mitochondria were isolated from 18 normal muscle biopsies and state 3 respiration rates measured with glutamate/malate, pyruvate/malate and succinate as substrates. In 13 experiments, reproducible respiration rates with adequate respiratory control ratios (RCR) and ADP/O ratios were obtained. Mean state 3 respiration rates of 280 ng-atoms 0 min-1 mg mitochondrial protein-1 (30 degrees C) with glutamate, 214 ng-atoms 0 min-1 mg mitochondrial protein-1 (30 degrees C) with pyruvate and 353 ng-atoms 0 min-1 mg mitochondrial protein-1 (30 degrees C) with succinate as substrates were higher than in most earlier reports. Selective uncoupling with alpha-glycerophosphate and data suggesting a partial site I deficiency were found in some experiments where RCR and ADP/O ratio measurements indicated a good preparation. Slow rates with all substrates with loose coupling were found in 3 studies where the mitochondria were clearly damaged during extraction. Guidelines for the evaluation of polarographic data in reports in the literature are suggested.